



= Delay Module

The `delay` module delays the processing of a request in a
non-blocking fashion.

The module is most useful for rate limiting reject responses.
Instead of having a specific "reject delay" configuration, it is
instead possible to have a policy that delays the response.

TIP: The module can also be used to introduce artificial jitter into
responses by adding random delays.

## xlat for delays

The module also registers an xlat function for delays

%delay(...)

This function takes a time-delta argument (or data which is converted to a time-delta), and will delay the given number of seconds.

.Example

```
%delay(0.2s)
```




## Configuration Settings



### Simple delay


delay:: How long to delay request processing for.



force_reschedule:: Whether the request should be rescheduled even if no
delay is needed.

Rescheduling the request pauses it momentarily, and
introduces a small delay.  It allows for processing of
other requests ahead of this one.  The result is a small
amount of "jitter" in responses, which can help avoid some
deterministic timings in the network.



relative:: Whether delay should be calculated relative to when
the request was received.

This configuration can be useful for rate limiting, as most
NAS will only allow a limited number of requests to be in
flight.

The default is `no`, which means that.



### Delaying Access-Reject packets

The `delay_reject` module should be used in a `send Access-Reject`
section, as the last module in that section. When `delay_reject`
is used there, the reject will be delayed for either
FreeRADIUS-Response-Delay seconds, or if that attribute does
not exist, then one second.

While the response is delayed, the server will continue processing
other requests.  It will simply set a timer to wake up and send the
response after the delay.

NOTE: We set `relative = yes` here.  That setting ensures that
if the server takes more than one second to process the request,
then the `delay_reject` module will not add *additional* delays.
Instead, this module will ensure that the `link:https://freeradius.org/rfc/rfc2865.html#Access-Reject[Access-Reject]` is sent
no earlier than one second after the `link:https://freeradius.org/rfc/rfc2865.html#Access-Request[Access-Request]` had been
received.


== Default Configuration

```
delay {
	delay = 1.0s
#	force_reschedule = no
#	relative = no
}
delay delay_reject {
	delay = "%{&reply.FreeRADIUS-Response-Delay || 1}"
	relative = yes
}
```
